Accept a buffer or a kernel for context properties and act on the associated kernel.
Remove support for cuda < 4.0.
Proper const for GpuArray_transfer().
Rework context handling in cuda_property to avoid the "context is so dead we can't even fetch it" problem, allowing better error messages.
New call api for kernels.  We no longer use the setarg model as it required keeping references to the passed-in buffer for a unknown amount of time, interfering with the memory management of the clients.

The new model also has the advantage that you only have to know the types of the arguments at creation time and they will be remembered.  There is currently no type checking apart from buffer which should be checked on debug builds.
Move the python bindings to the new call interface.  Reduction has problems that does not seem linked to this new interface.